Air conditioner for vehicles

ABSTRACT

An air conditioner for a vehicle includes a heat pump system for heating and cooling. The air conditioner includes a ventilation passage for ventilating air from a passenger compartment of the vehicle outside of the vehicle. An accelerating system is provided with the heat pump system for accelerating the evaporation of a refrigerant during air cooling or the condensation of a refrigerant during air heating by using involved energy recovered from air exhausted outside of said vehicle through the ventilation passage. Thereby, the air conditioner increases the heating and cooling ability and reduces the energy necessary for maintaining a constant temperature in the passenger compartment.

This application is a division of application Ser. No. 08/626,378, filedApr. 2, 1996, entitled AIR CONDITIONER FOR VEHICLES, now U.S. Pat. No.5,749,235 filed on May 12, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an air conditioning system,such as for use in cooling and heating passenger compartments inautomotive vehicles, and more particularly, to an air conditioningsystem having a heat exchanger accelerating system for more efficientlycooling and heating automobile passenger compartment.

2. Description of the Related Art

A heat pump circuit may be used in an automobile air conditioning systemto improve the cooling and heating efficiency of the system in theoutside air inlet mode of operation. For example, Japanese PatentApplication No. 62-181909 describes an automobile air conditioningsystem that includes a heat pump circuit. When the heat pump circuit isused for heating, a first heat exchanger is disposed in the passengercompartment and is used as a condenser. A second heat exchanger isdisposed in the engine compartment and is used as an evaporator.

FIG. 1 illustrates a heat pump-type automotive air conditioning system.Air conditioner 100 includes a variable displacement motor compressor 1,an external heat exchanger 3, and an internal heat exchanger 4. Air forair conditioning is conducted into the interior of the vehicle through aduct 10. External heat exchanger 3 is positioned outside of duct 10, andinternal heat exchanger 4 is positioned inside of duct 10.

First, second, third, and fourth openings of four-way valve 2 areconnected to the discharge port of compressor 1, a first port ofinternal heat exchanger 4, the suction port of compressor 1, and a firstport of external heat exchanger 3, respectively. A second port ofexternal heat exchanger 3 is connected to the inlet of a receiver 9 viaa first check valve 7. The outlet of receiver 9 is connected to internalheat exchanger 4 via a first expansion valve 5. A second expansion valve6 is provided between the outlet of receiver 9 and the second port ofexternal heat exchanger 3. Further, the second port of internal heatexchanger 4 is connected to the inlet port of receiver 9 via a secondcheck valve 8.

Duct 10 has an outside air inlet port and an inside air inlet port. Thebalance between outside air and inside air to be drawn into duct 10 isadjusted by a switching damper 12. A motor fan 11 is positioned in duct10 as a means for drawing outside air into the interior of the vehicle.

In FIG. 1, the solid arrows indicate the direction of refrigerant flowwhen the heat pump circuit is used for cooling air, and the dashedarrows indicate the direction of refrigerant flow when the heat pumpcircuit is used for heating. In operation, in response to a demand tocool passenger compartment, four-way valve 2 is switched (solid lines invalve 2) to configure the heat pump circuit as an air cooling system.

When air cooling is performed, the refrigerant is circulated fromcompressor 1 via four-way valve 2 to the first port of external heatexchanger 3, from the second port of external heat exchanger 3 to theinlet of receiver 9 via check-valve 7, from the outlet of receiver 9 viaexpansion valve 5 to the second port of internal exchanger 4, and fromthe first port of internal heat exchanger 4 via four-way valve 2 tocompressor 1, as shown by the solid line arrows in FIG. 1. The inside,e.g., recycled, or outside, e.g., fresh, air is introduced into duct 10through damper 12 and passes through internal heat exchanger 4 due tothe operation of motor fan 11. In this configuration, internal heatexchanger 4 is utilized as an evaporator. Consequently, the inside oroutside air exchanges heat with the refrigerant in internal heatexchanger 4, and the refrigerant vaporizes due to its absorption of heatfrom the inside or outside air. As a result, the inside or outside air,which is thus cooled, is blown into passenger compartment 13, wherebypassenger compartment 13 is cooled. Subsequently, the air in passengercompartment 13 is vented to the outside of the automobile throughventilation duct 14.

Alternatively, when air heating is performed, the refrigerant iscirculated from compressor 1 via four-way valve 2 to the first port ofinternal heat exchanger 4, from the second port of internal heatexchanger 4 via check valve 8 to the inlet of receiver 9, from theoutlet of receiver 9 via expansion valve 6 to the second port ofexternal heat exchanger 3, and from the first port of external heatexchanger 3 via four-way valve 2 to compressor 1, as shown by the dashedline arrows in FIG. 1. The inside or outside air again is introducedinto duct 10 through damper 12 and passes through internal heatexchanger 4 due to the operation of motor fan 11. In this configuration,internal heat exchanger 4 is utilized as a condenser. Consequently, theinside or outside air exchanges heat with the refrigerant in internalheat exchanger 4, and the refrigerant is condensed due to its loss ofheat to the inside or outside air in duct 10. As a result, the inside oroutside air, which is thus heated, is then blown into passengercompartment 13, whereby passenger compartment 13 is heated.Subsequently, the air in passenger compartment 13 is vented to theoutside of the vehicle through ventilation duct 14.

Thus, such air conditioning system results in the loss of energy,represented by the calories expended in heating or cooling air blowninto the passenger compartment, which the air that is vented outside ofthe vehicle includes implicitly. The air conditioning system loses thisenergy outside of the vehicle when the system exhausts unpleasant, e.g.,too hot or too cold, and stale air to the outside of the vehicle.Therefore, such heat pump systems consume additional energy tocompensate for this vented air.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a heatpump refrigeration system for motor vehicle which has improvedefficiency and superior heating and cooling abilities.

In one embodiment, the present invention discloses an air conditionerfor a vehicle including a heat pump system capable of heating or coolinga vehicle compartment. The air conditioner includes a ventilationpassage for conducting air in a vehicle compartment outside of thevehicle. The heat pump system includes an external heat exchangermounted outside the compartment; an internal heat exchanger mountedinside the compartment, which is coupled to the external heat exchanger;a compressor disposed in a refrigerant conduit, wherein the refrigerantconduit places the internal and external heat exchangers incommunication to transport refrigerant; and a valve mechanism positionedbetween the compressor and the internal and external heat exchangers andhaving at least two positions, a first position, which enablesrefrigerant to flow between the internal and external heat exchangers ina first direction, and a second position, which enables refrigerant toflow in a second direction opposite to the first direction. Anaccelerating system is provided within the heat pump system foraccelerating the condensation or the evaporation a refrigerant duringair heating or air cooling, respectively, by using energy recovered fromair being exhausted outside of the vehicle through the ventilationpassage. The accelerating system may include a first heat exchanger,which is positioned in parallel to the external heat exchanger andconnected to a second heat exchanger, which is disposed in theventilation passage for exchanging heat between a working fluid withair, which then is exhausted outside of the vehicle through theventilation passage, and a pump disposed between the first and secondheat exchangers for circulating the working fluid.

Other objects, features, and advantages will be apparent to persons ofordinary skill in the art in view of the following detailed descriptionof the invention and the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described with reference tothe appropriate figures, which are provided by way of example only, andare not intended to limit the scope of the present invention.

FIG. 1 is a schematic view of an air conditioner for vehicles includinga refrigerant circuit diagram according to an embodiment of the priorart.

FIG. 2 is a schematic view of an air conditioner for vehicles includinga refrigerant circuit diagram according to a first embodiment of thepresent invention.

FIG. 3 is a block diagram of an a control circuit of the air conditionerdepicted in FIG. 2.

FIG. 4 is a flowchart depicting steps for control of the thermal energyrecovery system depicted in FIG. 2.

FIG. 5 is a schematic view of an air conditioner for vehicles includinga refrigerant circuit diagram according to a second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With respect to FIG. 2, an air conditioner for a heat pump-typerefrigerant circuit is depicted in accordance with a first embodiment.The same numerals are used in FIG. 2 to denote corresponding elementsdepicted in FIG. 1. Thus, a further detailed explanation of thoseelements is here omitted.

In the embodiment of FIG. 2, air conditioner 200 includes a first heatexchanger 15 positioned in parallel to external heat exchanger 3 in arefrigerant circuit. First heat exchanger 15 includes refrigerantpassageway 15a exchanging heat with the refrigerant and heat mediumpassageway 15b for exchanging heat with the working fluid. Solenoidvalve 16 may be provided in the refrigerant circuit for closing andopening the path of the refrigerant into refrigerant passageway 15a offirst heat exchanger 17 which is disposed in ventilation duct 14 forrecovering the energy, e.g., the calories expended to heat or cool thevented air, which air is exhausted to the outside of the vehicle throughventilation duct 14. Second heat exchanger 17 is provided in workingfluid circuit 22 which connects first heat exchanger 15 with second heatexchanger 17. Circulating pump 18 is provided in working fluidpassageway 22 to circulate a cooling/heating medium, such as water orbrine, between second heat exchanger 17 and first heat exchanger 15.

Further, air conditioner 200 may include a first temperature sensor 19,such as a thermal switch or a thermistor, which is provided outside ofthe vehicle for measuring the outside air temperature. A secondtemperature sensor 20 is provided at a position upstream of first heatexchanger 15 for detecting the temperature of the cooling/heating mediumflowing into heat exchanger 15. Further, air conditioner 200 may includea plurality of valves for switching the flow of the refrigerant, as analternative to four-way valve 2.

FIG. 3 depicts a control circuit suitable for use in air conditioner200. An air conditioner switch 30, a conditioning temperature settingdevice 34, and a selector 31 for selecting an operating mode, e.g.,cooling or heating, are connected to a control unit 35, such as amicrocomputer. Air conditioning switch 30 initiates the operation of airconditioner 200. Conditioning temperature setting device 34 may have alever, buttons, or the like, for setting an air temperature to becontrolled, and the temperature for air conditioning may be selected andset by the operation of the conditioning temperature setting device 34.Selector 31 for selecting an operating mode may have a switch levercapable of changing the selection between a "cool" position and a "heat"position.

Referring to FIGS. 3 and 4, control unit 35 may have a CPU, ROMs, RAMs,and the like, and suitable software for the control of switchingconditions of the solenoid valves, as well as software for the controlin the ROMs. Control unit 35 sends control signals to a compressordriving circuit 36, a pump driving circuit 37, a four-way drivingcircuit 38, a solenoid valve driving circuit 39, and a fan drivingcircuit 40. Compressor driving circuit 36 controls the rotational speedof compressor 1 in response to the rotational speed signal sent fromcontrol unit 35. Pump driving circuit 37 controls the activation anddeactivation of pump 18 in response to the signals from air conditionerswitch 30. Solenoid valve driving circuit 39 controls the opening andclosing of the solenoid valve 2 in response to the detected signals oftemperature sensors 19 and 20. Fan driving circuit 40 controls thevolume of air supplied by motor fan 11 in response to an air volumesignal sent from control unit 35.

In the cooling mode of operation, four-way valve 2 is switched asindicated by the solid lines in FIG. 1. In such a condition, compressor1 and pump 18 are activated. The refrigerant discharged from compressor1 flows to external heat exchanger 3 and is condensed therein. Thecondensed refrigerant flows to first expansion valve 5 and to internalheat exchanger 4 through first check valve 7 and receiver 9 and isevaporated therein. The evaporated refrigerant finally flows intocompressor 1 through four-way valve 2. Thus, the cooling of passengercompartment 13 may be accomplished utilizing the heat-absorbing actionof the refrigerant at internal heat exchanger 4. The air in passengercompartment 13 is then continuously vented to the outside of the vehiclethrough ventilation duct 14. Second heat exchanger 17 recovers energywhich this vented air implicitly includes, so that the heating/coolingmedium within second heat exchanger 17 exchanges heat with the airpassing through ventilation duct 14. Further, energy recovered by secondheat exchanger 17 and carried by the heating/cooling medium iscirculated to working fluid passageway 15b of first heat exchanger 15through working fluid circuit 22 by pump 18.

Referring to FIG. 4, when working fluid temperature "Tw" detected bythermal sensor 20 is less than outside air temperature "Ta" detected bythermal sensor 19 which is placed adjacent external heat exchanger 3 soas to be upstream of air flowing over the outside of engine compartment.Consequently, when working fluid temperature "Tw" is in the specifiedrange, such that the refrigerant within first heat exchanger 15 issufficiently condensed, solenoid valve 16 is opened, and a portion ofthe refrigerant discharged from compressor 1 flows into refrigerantpassageway 15a of first exchanger 15.

Further, in the heating mode of operation, four-way valve 2 is switchedas indicated by the dashed lines in FIG. 2. In such a condition,compressor 1 and pump 18 are again activated. The refrigerant dischargedfrom compressor 1 flows to internal heat exchanger 4 and is evaporatedtherein. The evaporated refrigerant then flows to second expansion valve6 and to external heat exchanger 3 through second check valve 8 andreceiver 9 and is condensed therein. The condensed refrigerant finallyflows into compressor 1 through four-way valve 2. Thus, the heating ofpassenger compartment 13 may be accomplished by the radiating action ofthe refrigerant at internal heat exchanger 4. The air within passengercompartment 13 is then continuously vented outside of the vehiclethrough ventilation duct 14. Second heat exchanger 17 recovers energywhich this vented air implicitly includes, so that the heating/coolingmedium within second heat exchanger 17 exchanges heat with the airpassing through ventilation duct 14. Further, energy recovered by secondheat exchanger 17 and carried by the heating/cooling medium iscirculated to working fluid passageway 15b of first heat exchanger 15through working fluid circuit 22 by pump 18.

In addition, when working fluid temperature "Tw" detected by thermalsensor 20 is greater than outside air temperature "Ta" detected bythermal sensor 19, that is when working fluid temperature "Tw" is in thespecified range, such that the refrigerant within first heat exchanger15 is sufficiently evaporated, solenoid valve 16 is opened, and aportion of the refrigerant discharged from compressor 1 flows intorefrigerant passageway 15a of first exchanger 15. Alternatively, if airconditioner 200 is not provided with solenoid valve 16, the portion ofthe refrigerant discharged from compressor 1 may constantly flow intorefrigerant passageway 15a of first heat exchanger 15.

Thus, second heat exchanger 17 recovers energy which the air exhaustedto the outside of the vehicle through ventilation duct 14 implicitlyincludes. In the cooling mode of operation, such an air conditioningsystem accelerates the condensation of the refrigerant therein over thatin heat pump system. In the heating mode of operation, such an airconditioning system accelerates the evaporation of the refrigeranttherein over that in heat pump system. Therefore, such an airconditioning system increases the heating and cooling ability byobtaining high endothermic and radiating efficiency. As a result, such asystem may reduce the energy expenditure necessary to maintain aconstant temperature in the passenger compartment of the vehicle.

Referring to FIG. 5, a second embodiment of the present invention isdepicted. Elements similar to those discussed above are designated withthe same reference numerals, and the following discussion focusesprimarily on the features of the second embodiment.

An external heat exchanger 33 is disposed in ventilation duct 14 forrecovering energy from air which is exhausted outside of the vehiclethrough ventilation duct 14. Solenoid valve 36 may be provided in therefrigerant circuit for closing and opening the path of the refrigerantflowing into external heat exchanger 33. In addition, second temperaturesensor 50 is provided at a position upstream of external heat exchanger33 for detecting the temperature of the refrigerant flowing intoexternal heat exchanger 33. Therefore, external heat exchanger 33 mayrecover energy which the air exhausted to the outside of the vehiclethrough ventilation duct 14 implicitly includes. In the cooling mode ofoperation, such an air conditioning system accelerates the condensationof the refrigerant therein over that in heat pump system. In the heatingmode of operation, such an air conditioning system accelerates theevaporation of the refrigerant therein over that in heat pump system. Inthis embodiment, substantially similar advantages to those obtained inthe first embodiment may be achieved.

This invention has been described in detail in connection with aplurality of embodiments, but these embodiments are merely exemplary,and the invention is not to be construed as limited thereto. It will beapparent to those skilled in the art that other variations ormodifications may be made within the scope of the invention as definedby the following claims.

What is claimed is:
 1. An air conditioner for a vehicle comprising:aheat pump system for heating and cooling and including a refrigerantcircuit and a ventilation passage for venting air from a passengercompartment of said vehicle to outside of said vehicle, wherein saidheat pump system includes a first external heat exchanger mountedoutside said passenger compartment and an internal heat exchangermounted inside said passenger compartment and coupled to said externalheat exchanger; accelerating means for accelerating evaporation of arefrigerant during air cooling and condensation of said refrigerantduring air heating by recovering and using energy from air exhaustedoutside of said vehicle through said ventilation passage, wherein saidaccelerating means includes a second external heat exchanger of saidheat pump-type refrigerant circuit, and a valve for selectively couplingsaid first external heat exchanger and said second external heatexchanger; and a control means coupled to said valve, said control meansincluding a first sensor that detects a first temperature of air outsidesaid vehicle and a second sensor that detects a second temperature ofsaid refrigerant, and opens said valve during air cooling when saidsecond temperature is less than said first temperature, and closes saidvalve during air heating when said second temperature is greater thansaid first temperature.
 2. The air conditioner of claim 1, wherein saidsecond external heat exchanger is disposed in said ventilation passagefor exchanging heat with air exhausted outside of said vehicle throughsaid ventilation passage.
 3. The air conditioner of claim 1, whereinsaid heat pump system further includes a compressor disposed in arefrigerant circuit, said refrigerant circuit placing said external heatexchanger in fluid communication with said internal heat exchanger topermit refrigerant flow between said external and internal heatexchangers, a valve coupling said compressor and said external andinternal heat exchangers, wherein said valve has at least two positions,a first position which enables refrigerant to flow to said external andinternal heat exchangers in a first direction and a second positionenabling refrigerant to flow in a second direction opposite to saidfirst direction, and wherein said second external heat exchangerdisposed in said ventilation passage exchanges heat between saidrefrigerant and air exhausted outside of said vehicle through saidventilation passage.
 4. The air conditioner of claim 3, wherein saidcompressor is operated by an electric motor.